The present invention relates to ignition coils for ignition systems for igniting air-fuel mixtures, and particularly for use in systems using capacitors for storing higher levels of ignition energy, i.e. high energy capacitive discharge ignition systems, and for delivering the energy in the form of a rapidly pulsing (multi-strike) sequence of spark pulses.
Considerable research has been conducted on ignition systems for internal combustion engines for improving their capability to ignite air-fuel mixtures. More specifically, during the past few decades, there has been work done on improving the ability of ignition systems to ignite air-fuel mixtures with poor ignition characteristics, especially of the inherently cleaner and more efficiently burning leans air-fuel mixtures.
Much of the prior art work on so called high energy ignition has focussed on alternative approaches other than coil design for delivering high ignition energy. Little attention has been given to improving the actual coil design, particularly in view of the recent development of the high efficiency, voltage doubling, low turns ratio coil principle disclosed in U.S. Pat. No. 4,677,960 referred to hereinafter as the Voltage Doubling Coil principle, or Doubling principle for short.
Prior art work on spark ignition, including ignition coils, are numerous, and for example, are summarized in Edward F. Obert's book, "Internal Combustion Engines and Air Pollution", pp. 532 to 566, Spark-Ignition Engines, Intext Educational Publishers, 1973. The work reported by Obert, and the work published since then, including the coil design presented in the above patent, are based on well established principles of designing coils by either winding the primary and secondary windings essentially concentrically, or on different arms of a closed magnetic core for high leakage inductance. Included are various ways of performing the winding, especially the much longer secondary winding, and these are well known to one skilled in the art.